Controllable radioactive voltage charging devices



' Och 23, -1956 P. RAPPAPORT CONTROLLABLE RADIOACTIVE VOLTAGE CHARGING DEQJICES Filed Oct. 1, 1952 Pam. RHPPHPDRT R. M M. n, m i M., w fr, f K W i i a j M M /w Mi f u /f M W w Z a ,//m ,W at l0 WM. 4, 7e 0 4 wv. /z n i w M. am. w W7 o op WW m w w 407 Z AQ QQ MM 2,768,313 Patented ocr. 23, 195e CONTROLLABLE VRADIOACTIV E VCHARGING DEVICES 8 Claims. (Cl. S10-3) VOLTAGE This invention relates generally to voltage chargers and more particularly to an improved voltage charging device utilizing a radioactive isotope and having a controllable output voltage.

In the prior art, voltage charging or voltage generating devices have been devised in which a radioactive source of charged particles is positioned in a vacuum and produces high energy charged particles which subsequently are collected to establish an electric potential. The use of a vacuum was necessary to prevent gas ionization between the radiation source and a collector electrode for collecting the charged particle radiations. Such ionization would causea substantial if not complete reduction ofthe electrical charge desired. However, in a copending application Serial No. 177,015 tiled August l, 1950, by Ernest G. Linder radioactive voltagercharging apparatus is described and claimed wherein comparatively low potentials may be established in a normal atmosphere. In said application a dielectric material is interposed between the radiation source and the collector, the dielectric material preventing the ow of low energy ionized particles therebetween which would tend to reduce the potential to which the device charges.V

While the Linder apparatus is effective in affording voltage charging in air or other atmospheres, thedevice inherently charges to some relatively high final Voltage which is afunction, for example, of the quantity and type of radioactive isotope used, the conductivity and thickness `of the dielectric material, and other. factors. The voltage thus derived is Vhigh (of the order of several thousand volts): However, lmost fields of application for such devices require substantially lower voltages. These lower and desired voltages, rather than the voltage to which the ,device naturally charges, may be" achieved in one instance by utilizing voltage dividers. vTo achieve such voltages, however, relatively expensive dividers comprising resistors having resistances ofy the Vorder 1012 to 1014 ohms may be required. Since such resistors are not readily attainable at many different specified values, it is extremely difficult to obtain a particular desired output voltage. Also, such resistors are bulky and considerably increase the overall size of the charging apparatus.

According to the instant invention, an improved lo-w voltage radioactive charging device is disclosed and claimed in which the output voltage of the device may be limited as desired by providing a controlled ion leakage path intermediate the radiation source and the collector electrode. This ion leakage path etfectively shunts the charger and comprises an aperture located in the dielectric material and in the path of the high energy charged particles emitted by the radiation source. The equivalent resistance of the ionized column of gas contained within the apertured dielectric is determined by the aperture geometry and may be readily controlled.

An object of the invention is to provide an improved low voltage radioactive voltage generating device.

,Another object of the invention is tovprovide a low 2 voltage radioactive charging device having a controllable output voltage.

Another object of the invention is to provide an improved low voltage radioactive charger in which various specified voltages are readily attainable.

A further object of the invention is to provide an 'irn-v proved low voltage radioactive voltage generating device which is simple in structure and inexpensive to manufacture.

A further object is to provide an improved low voltage radioactive voltage charging device having an extensive field of applicability. Y

The invention will be described in detail with reference. to the accompanying drawing in which;

Figure l is a schematic diagram of a low voltage radioactive voltage charging device, according to the invention;

Figure 2 is a graph illustrating the charging rates and limiting voltages of devices having ,different ion leakage paths which devices are fabricated in accordance with the invention; and

Figure 3 is a schematic diagram of a modification of the apparatus of Figure l.

Similar reference characters are applied to similar elements throughout the drawing.

Referring to Figure l, a source 11 capable of emitting high energy radioactive charged particles is mounted on 'a conductive support member 13. In the present example it will be assumed that the radioactive isotope employed is strontium, a beta particle emitter. It will be recognized, however, that other beta particle emitters and other types of charged particle emitters also may be employed. Spaced from the support electrode 13 is acol. lector electrode 15 which may be formed from some `sui-table material such as aluminum. Intermediate the support electrode 13 and the collector electrode 15 a dielect-ric sheet or film 17 is disposed, the dielectric sheet comprising, for example, a sheet of polystyrene having an aperture 19 located in the travel path of a portion of the beta particles emitted by the source 1-1.

In operation: The high energy negatively charged beta particles emitted by the source 11 pass through 'the sup-4 port electrode 13 and through the dielectric 17, eachy of which have low beta ray absorption, to the collector elect-rode 15 Where they are absorbed almost completely to charge the electrode 15 to some negative with respect to the and of support 13 therefor. The electric energy of this potential may be utilized to supply current and hence power to a desired utilization circuit 21. example it will be seen that the source 11 and electrodes 13, 17, and 15 are illustrated as being in intimate contact with each othersuch that substantially no gas spiace exists 1between adjacent elements. Thus limi-ted ionization oc curs in the aperture space and there is only moderate discharge of the potential developed between the source and the collector electrodes. Although some ions may be formed within the dielectric 17, by bombardment-inducedconductivity, this is not significant since the effective resistance of the dielectric material under bombardment is quite large. This contact arrangement is not essential, however, since in some instances a spaced arrangement may be preferred. The spaced arrangement aords smaller values of capacity between electrodes 13 and 15 and hence higher charging rates.

As described previously, the Linder voltage charger normally charges t-o some ultimate and relatively high potential which is a function of a number of factors. This high voltage is reduced readily to a lower and more useful value, in accordance with the invention, by means of the aperture 19 located in the dielectric material 17 and situated in the travel path of a portion of the beta radina-l voltage which is potential of the source 11` In the instant ation. A gas (air, for example) is contained within the connes of the dielectric material detning the aperture 19 and is ionized by the high energy radiation. If desirable the efficiency of such ionization may be enchanced by means of a magnetic eld, indicated generally by the arrow H. This ionized column of gas intermediate the source 1-1 and the collector 15 acts as a resistor effectively shunting the voltage charger reducing the output voltage which it normally tends to develop. :For the conditions illustrated in Figure 2, a .053 diameter hole causes the output voltage of the device to limit at 32 volts. lf the dielectric material aperture 19 is made smaller, say .046, the res-istance of the ionized column effectively shunting the charging is increased and the output potential thereof is approximately 110 volts. Other data are given for apertures having other diameters. ilt will be recognized, however, that other aperture configurations and geometries may be used to achieve desired resistances for obtaining output voltags as required.

Referring to Figure 3, a further embodiment of the invention is shown in which a single voltage generating or voltage charging device is adapted for supplying a wide range of output voltages. To this end the dielectric material 17 may be prepared to provide a threaded opening 23 adapted to receive a probe 25 longitudinally adjustable therein. The probe 25 preferably is formed from the same material as the dielectric sheet 17. With the probe 25 completely traversing and clos-ing the aperture 19, it will be seen that the eftective shunt resistance of the ionized gas column is high and the corresponding output voltage of the device is high. By progressively increasing the aperture Asize at the point wherein the probe traverses the aperture, the equivalent resistance of the gas column decreases and the output voltage of the device also decreases. By suitably shaping and sizing the probe 25 and by adjusting the relative position of the probe in the aperture substantially any desired output voltage readily may be obtained. Although the probe position is illustrated as being manually adjustable, it is pointed out that the probe position may be actuated in response to varying mechanical or electric-al signal intelligence resulting in current being supplied to the load circuit Z1 in an alternating lashion.

Thus the instant invention is directed t-o a new and improved radioactive voltage charging or voltage generating device having a controllable output voltage. The device is structurally simple and easy to fabricate. Also, a wide range of voltages are attainable which voltages are stable over extended periods of time and may be varied at will.

What is claimed is:

l. A voltage generating device comprising, a source of high energy charged particle emission, an electrode for collecting said charged particles to establish an electric potential relative to said source, anda controllable electricalv charge leakage path. disposed intermediate said source i and said electrode for controlling the level of said potentia-l.

2. A voltage generating device comprising, a source of high energy charged particle emission, an electrode for collecting said charged particles to establish an electric potential relative to said source, and a controllable electrical charge leakage path comprising an ionizable gaseous region disposed intermediate said source and said electrode for controlling the level of said potential.

3. A voltage generating device as claimed in claim 2- including means for utilizing the electric energy of said potential.

4. A voltage generating device comprising, a primary source of high energy charged particle emission, an electrode for collecting said charged particles to establish an electric potential relative to said source, and an apertured dielectric member disposed intermediate said source and collector for providing a controlled electrical charge leakage path for controlling the level of said potential.

5. A voltage generating device comprising, a primary source of high energy charged particle emission, a collector elec-trode for collecting said charged particles yto establish an electric potential relative to said source, and a dielectric member including an aperture disposed intermediate said source and said collector electrode, the con-y nes of said dielectric member defining said aperture con taining a gaseous medium capable of being ionized by a portion of said charged particle emission to provide a charge leakage path for cont-rolling the level of said potential.

6. A voltage generating device comprising, a primary source of high energy radioactive charged particle emission, an electrode for supporting said charged particle source, a collector electrode spaced from said source for collecting said charged particles to establish an electric potential relative to the potential of said source, andl an apertured dielectric member disposed intermediate and in contact with said support and collector electrodes for containing a gas capable of being ionized by said charged particle radiation for controlling the level of said potential. v

7. A voltage generating device as claimed in claim 2 including meansfor controlling the geometry of said ionized gaseous region to control the level of said' established potential.

8. A voltage generating device as claimed in claim 5 including a dielectric probe adjus-tably adapted to traverse said aperture to control the equivalent resistance of said gaseous medium.

Linder Aug. 1, 1950 Linder May 29, 1951 

